Typical “Drop on Demand” ink jet devices rely on ink having sufficient low surface energy to properly wet a substrate and spread evenly over the surface of the substrate. Ultraviolet (UV) inks are typically in the 34-36 dynes/cm range, due in part to the chemistry being used and the need for reasonably high surface tension of the ink to provide good jetting properties in the Drop on Demand ink jet system.
Many of the materials that are desirable to be printed on, other than plain paper, have very low surface energy materials, such as an ultraviolet (UV) varnish disposed on them, or they are made from a high density polyethylene or a polypropylene. These polymer based materials or varnished materials typically have surface energies of less than 30 dynes/cm. Accordingly, the use of a typical ink on a difficult to print surface yields a non-wettable situation resulting in print quality deficiencies, such as white lines, holes in print, or very high ink thickness.
Solutions have been found in the traditional offset printing industry to pre-treat a surface, such as using a corona discharge or an ion plasma system. The use of these processes in ink jet printing can cause some benefits, but can also create negative effects if over-used, by reacting static forces or ionic charges that are significant problems to the charge plate of the printhead. Use of a strong pretreatment on high surface energy materials can create excessive wetting causing significant bad print quality issues, such as feathering or “exploded” drops.
A need exists for a process in the digital ink jet technology field that is able to change simply and easily the imprinting parameters to accommodate the needs of the specific substrate material that is being printed. A need exists for a method that yields consistently good print quality on a wide variety of materials. Due to a variety of ink jet and ink issues, the goal has never been successfully accomplished in the current art.
The present embodiments described herein were designed to meet these needs.